Problems persist in KQueueSelectorProvider (Mac) in 7u6 ea (original) (raw)

David M. Lloyd david.lloyd at redhat.com
Fri Aug 10 16:36:39 PDT 2012

We're consistently seeing issues under load on Mac with KQueueSelectorProvider.

There are two possibly related symptoms: the KQueueSelectorImpl is going into a mode where select() does not block, despite the continued emptiness of the selected key set; and FileDispatcherImpl#preClose0 is hanging, presumably in dup2(), trying to close a socket.

My current hypothesis that some evil race condition exists and is being tripped between kqueue and dup2 (a relatively rare way to close a socket, at least until NIO came along I guess). My thought though is that sockets should not be preclosed this way: instead it would be better to use shutdown(fd, SHUT_RDWR), which would effectively preclose the socket and hopefully dodge this issue.

I'm hopefully going to have time to try out a patch which does this, but I'm taking a couple weeks off starting tonight so I may not have time, so we shall see.

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